It has long been considered desirable for governmental and commercial purposes to have a high altitude "platform" from which a payload (e.g. radiation sensors or other devices) can operate.
My prior U.S. Pat. No. 4,697,761, granted Oct. 6, 1987, discloses an aircraft which is powered by solar cells located on the upper surfaces of the aircraft, and by long wave infrared radiation responsive cells located on the lower surfaces of the aircraft. My system as disclosed in that patent contemplated that the solar cells would supply much more power while exposed to the sun, than the infrared cells. Batteries or fuel cells were used to store the excess power provided by the solar cells for use during periods when the sun was not shining. The requirement for batteries adds considerable weight to the aircraft, and the need for power supply switching circuitry added complexity and increased the possibility of system failure. The resultant payload for the aircraft was therefore somewhat less than optimum; and the required system power circuitry involving solar power, infrared power, battery power, and combinations thereof, was somewhat more complex than would be desired. Further, the need to rely on solar energy makes the system less capable than would be desired, because the incident solar radiation at the higher (and lower) latitudes is significantly reduced for an aircraft with horizontal solar arrays. Erecting the solar arrays to a more vertical orientation to maximize the incident solar radiation increases airframe weight penalties for hinges, erecting mechanisms and controls, thus detracting from payload weight.
Accordingly, principal objects of the present invention include providing a reliable lightweight aircraft, which is independent of solar energy, requires no array erecting mechanism, and which has relatively high payload and simplified electronics.